/*
 * Copyright 2010 Antoine Toulme
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package voldemort.serialization.avro;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

import org.apache.avro.Schema;
import org.apache.avro.file.DataFileStream;
import org.apache.avro.file.DataFileWriter;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DatumWriter;

import voldemort.serialization.SerializationException;
import voldemort.serialization.Serializer;

/**
 * Avro serializer that uses the generic representation for Avro data. This
 * representation is best for applications which deal with dynamic data, whose
 * schemas are not known until runtime.
 * 
 * @see http://hadoop.apache.org/avro/docs/current/api/java/org/apache/avro/generic/package-summary.html
 */
public class AvroGenericSerializer implements Serializer<Object> {

    private final Schema typeDef;

    /**
     * Constructor accepting the schema definition as a JSON string.
     * 
     * @param schema a serialized JSON object representing a Avro schema.
     */
    public AvroGenericSerializer(String schema) {
        typeDef = Schema.parse(schema);
    }

    public byte[] toBytes(Object object) {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        DataFileWriter<Object> writer = null;
        try {
            DatumWriter<Object> datumWriter = new GenericDatumWriter<Object>(typeDef);

            writer = new DataFileWriter<Object>(datumWriter).create(typeDef, output);
            writer.append(object);
        } catch(IOException e) {
            throw new SerializationException(e);
        } finally {
            AvroUtils.close(writer);
        }
        return output.toByteArray();
    }

    public Object toObject(byte[] bytes) {
        ByteArrayInputStream input = new ByteArrayInputStream(bytes);
        DataFileStream<Object> reader = null;
        try {
            DatumReader<Object> datumReader = new GenericDatumReader<Object>(typeDef);
            reader = new DataFileStream<Object>(input, datumReader);
            return reader.next();
        } catch(IOException e) {
            throw new SerializationException(e);
        } finally {
            AvroUtils.close(reader);
        }
    }
}
